Here in the States, if you can look in some specialty food shops (such as the one I used to own), you might be able to find them (presuming you knew what they are in the first place).
Curious Little Factoid: One of the reasons they never got a toe-hold here in the States was their name. Our FDA some long time ago ruled that the term "digestive" was a "medical claim" that had never been proven.
They're not antacids at all but pretty tasty plain-ish cookies. We had a hard time keeping McVitties and Hob Nobs in stock; we used to joke that their recipes called for a little smidge of crack.
I'm afraid there's no real American equivalent that I could suggest for your article.